共查询到20条相似文献,搜索用时 187 毫秒
1.
Nina-Luisa Michels Agnieszka Kapałka A.A. Abd-El-Latif Helmut Baltruschat Christos Comninellis 《Electrochemistry communications》2010,12(9):1199-1202
Electrochemical oxidation of ammonia (NH3 and NH4 + ) on boron-doped diamond (BDD) electrode was studied using differential electrochemical mass-spectrometry (DEMS) and chronoamperometry. Electro-oxidation of ammonia induces inhibition of the oxygen evolution reaction (OER) due to adsorption of the ammonia oxidation products on the BDD surface. The inhibition of the OER enhances ammonia electro-oxidation, which becomes the main reaction. The amino radicals, formed during ammonia oxidation, trigger a reaction chain in which molecular oxygen dissolved in solution is involved in the ammonia electro-oxidation. Nitrogen, nitrous oxide, and nitrogen dioxide were detected as the ammonia oxidation products, with nitrogen being the main gaseous product of the oxidation. 相似文献
2.
E. Moran C. Cattaneo H. Mishima B. A. López de Mishima S. P. Silvetti J. L. Rodriguez E. Pastor 《Journal of Solid State Electrochemistry》2008,12(5):583-589
Ammonia electro-oxidation on Pt–Ir alloys has been studied applying cyclic voltammetry and differential electrochemical mass
spectrometry (DEMS), and the results were compared with pure Pt. Bimetallic alloys were prepared by electrodeposition and
characterized using X-ray diffractometry (XRD) and Auger spectroscopy, before and after oxidation of ammonia. Pt/Ir atomic
composition was 70:30 obtained from 1:1 solutions. Substitution alloys were established where Ir atoms replace Pt positions
in the face-centered cubic structure. Preferential crystal orientations were detected in the electrodeposits with the development
of a crystallographic texture. DEMS showed that N2 is the main product during ammonia oxidation for both Pt and Pt–Ir, but the formation of nitrogen oxides is observed for
E > 0.8 VRHE. The yield of N2 is higher for the alloy, which also displays lower poisoning of the surface when increasing ammonia concentration. These
results confirm Pt–Ir alloys as alternatives to Pt electrodes concerning ammonia oxidation. Finally, it was observed that
XRD patterns, as well as texture coefficient values, change after using the electrodeposits for ammonia oxidation, with the
less compact planes the more affected ones.
Dedicated to Prof. Dr. Teresa Iwasita on the occasion of her 65th birthday in recognition of her numerous contributions to
interfacial electrochemistry. 相似文献
3.
Investigations of the dependence on the potential of the anodic oxidation of carbon electrodes using differential electrochemical mass spectroscopy (DEMS) show that pure carbon is oxidized only at potentials higher than 0.9 V (RHE) (with CO2 and, to a lesser extent, CO being the main products), and that Pt activation catalyzes the oxidation of a COsurf surface layer to CO2 at potentials between 0.6 and 0.8 mV (RHE), with the COsurf being formed on the carbon at E>0.3 V (RHE).It is assumed that the Pt-induced carbon corrosion occurs in the neighbourhood of the Pt-sites, thus damaging the Pt to carbon contact. Surface segregation of Pt-clusters and a loss of catalytic activity is the result. 相似文献
4.
Mieczys?aw M?kosza Krystyna Kamieńska-Trela Maciej Paszewski Ma?gorzata Bechcicka 《Tetrahedron》2005,61(50):11952-11964
Oxidative nucleophilic substitution of hydrogen (ONSH) in nitroarenes with carbanion of isopropyl phenyl acetate gives various products depending on the conditions and oxidant. The reaction carried out in liquid ammonia and KMnO4 oxidant gives iso-propyl α-hydroxy-α-nitroarylphenylacetates formed via hydroxylation of the initial ONSH products. In some cases additionally dimeric, trimeric and tetrameric products are formed. In THF and Bu4N+MnO4− or DDQ oxidants simple ONSH products are formed whereas oxidation by dimethyl dioxirane (DMD) gave iso-propyl hydroxyaryl phenyl acetates. The dimeric and trimeric products are apparently formed via coupling of nitrobenzylic radicals generated in course of oxidation with nitrobenzylic carbanions of the ONSH products. 相似文献
5.
E. Pastor S. Wasmus T. Iwasita M.C. Arvalo S. Gonzlez A.J. Arvia 《Journal of Electroanalytical Chemistry》1993,350(1-2)
The electrochemical behavior of n-propanol (n-PrOH) on polycrystalline Pt in acid solutions was investigated using in situ Fourier transform infrared spectroscopy (FTIRS) and on line differential electrochemical mass spectrometry (DEMS). The main products of n-PrOH oxidation are CO2, propanal and propionic acid. Different types of adsorbates with one, two or three C atoms were detected. Ethane and propane are produced from n-PrOH adsorbates during potential cycling in the H-adatom potential region. An increase in the quantity of adsorbed CO was observed after hydrogenation of n-PrOH adsorbates. 相似文献
6.
Aleksandra Jankowska Agata Chopek Andrzej Kowalczyk Magorzata Rutkowska Marek Michalik Shiquan Liu Lucjan Chmielarz 《Molecules (Basel, Switzerland)》2020,25(23)
Spherical MCM-41 with various copper and iron loadings was prepared by surfactant directed co-condensation method. The obtained samples were characterized with respect to their structure (X-ray diffraction, XRD), texture (N2 sorption), morphology (scanning electron microscopy, SEM), chemical composition (inductively coupled plasma optical emission spectrometry, ICP-OES), surface acidity (temperature programmed desorption of ammonia, NH3-TPD), form, and aggregation of iron and copper species (diffuse reflectance UV-Vis spectroscopy, UV-Vis DRS) as well as their reducibility (temperature programmed reduction with hydrogen, H2-TPR). The spherical MCM-41 samples modified with transition metals were tested as catalysts of selective catalytic reduction of NO with ammonia (NH3-SCR). Copper containing catalysts presented high catalytic activity at low-temperature NH3-SCR with a very high selectivity to nitrogen, which is desired reaction products. Similar results were obtained for iron containing catalysts, however in this case the loadings and forms of iron incorporated into silica samples very strongly influenced catalytic performance of the studied samples. The efficiency of the NH3-SCR process at higher temperatures was significantly limited by the side reaction of direct ammonia oxidation. The reactivity of ammonia molecules chemisorbed on the catalysts surface in NO reduction (NH3-SCR) and their selective oxidation (NH3-SCO) was verified by temperature-programmed surface reactions. 相似文献
7.
Tieliang Li Shuhe Han Dr. Yuting Wang Jin Zhou Prof. Bin Zhang Prof. Yifu Yu 《Angewandte Chemie (International ed. in English)》2023,62(19):e202217411
As a potential substitute technique for conventional nitrate production, electrocatalytic nitrogen oxidation reaction (NOR) is gaining more and more attention. But, the pathway of this reaction is still unknown owing to the lack of understanding on key reaction intermediates. Herein, electrochemical in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and isotope-labeled online differential electrochemical mass spectrometry (DEMS) are employed to study the NOR mechanism over a Rh catalyst. Based on the detected asymmetric NO2− bending, NO3− vibration, N=O stretching, and N−N stretching as well as isotope-labeled mass signals of N2O and NO, it can be deduced that the NOR undergoes an associative mechanism (distal approach) and the strong N≡N bond in N2 prefers to break concurrently with the hydroxyl addition in distal N. 相似文献
8.
Symmetric and non-symmetric 2-(N-H, N-methyl, N-ethylenyl and N-aryl)guanidinebenzothiazoles were synthesized from the reaction of ammonia, methylamine, pyrrolidine and aniline with dimethyl benzo[d]thiazol-2-yl-carbono-dithioimidate (5) as intermediate. The products were characterized by 1H-, 13C-NMR spectroscopy and three of them by X-ray diffraction analysis. HN-phenyl protons formed intramolecular hydrogen bonds that assist the stereochemistry of the second substituent, whereas the HN-alkyl protons were involved in intermolecular hydrogen bonding. 相似文献
9.
Yuting Wang Wei Zhou Ranran Jia Yifu Yu Bin Zhang 《Angewandte Chemie (International ed. in English)》2020,59(13):5350-5354
Unveiling the active phase of catalytic materials under reaction conditions is important for the construction of efficient electrocatalysts for selective nitrate reduction to ammonia. The origin of the prominent activity enhancement for CuO (Faradaic efficiency: 95.8 %, Selectivity: 81.2 %) toward selective nitrate electroreduction to ammonia was probed. 15N isotope labeling experiments showed that ammonia originated from nitrate reduction. 1H NMR spectroscopy and colorimetric methods were performed to quantify ammonia. In situ Raman and ex situ experiments revealed that CuO was electrochemically converted into Cu/Cu2O, which serves as an active phase. The combined results of online differential electrochemical mass spectrometry (DEMS) and DFT calculations demonstrated that the electron transfer from Cu2O to Cu at the interface could facilitate the formation of *NOH intermediate and suppress the hydrogen evolution reaction, leading to high selectivity and Faradaic efficiency. 相似文献
10.
Yao Yao Shangqian Zhu Haijiang Wang Hui Li Minhua Shao 《Angewandte Chemie (International ed. in English)》2020,59(26):10479-10483
Rh is a promising electrocatalyst for the nitrogen reduction reaction (NRR) given its suitable nitrogen‐adsorption energy and low overpotential. However, the NRR pathway on Rh surfaces remains unknown. In this study, we employ surface‐enhanced infrared‐absorption spectroscopy (SEIRAS) and differential electrochemical mass spectrometry (DEMS) to study the reaction mechanism of NRR on Rh. N2Hx (0≤x≤2) is detected with a N=N stretching mode at ≈2020 cm?1 by SEIRAS and a signal at m/z=29 by DEMS. A new two‐step reaction pathway on Rh surfaces is proposed that involves an electrochemical process with a two‐electron transfer to form N2H2 and its subsequent decomposition in the electrolyte producing NH3. Our results also indicate that nitrate reduction and the NRR share the same reaction intermediate N2Hx. 相似文献
11.
Faiza Nessark Mohamed Eissa Abdoullatif Baraket Nadia Zine Belkacem Nessark Ahmed Zouaoui Joan Bausells Abdelhamid Errachid 《Electroanalysis》2020,32(8):1795-1806
In the present study, we developed a novel label‐free capacitance impedimetric immunosensor based on the immobilization of the human monoclonal antibody anti‐interleukin‐10 (anti‐IL‐10 mAb) onto polypyrrole (PPy)‐modified silicon nitride (Si3N4) substrates. The immunosensor was used for the detection of the recombinant interleukin‐10 antigen (rh IL‐10) that may be secreted in patients at the early stage of inflammation. The immunosensor was created by chemical deposition of PPy conducting layer on pyrrole?silane (SPy)‐treated Si/SiO2/Si3N4 substrates (Si/SiO2/Si3N4?SPy), followed by anti‐IL‐10 mAb immobilization through carboxyl‐functionalized diazonium (CMA) protocol and carbodiimide chemistry. The surface characterization and the biofunctionalization steps were characterized by SEM, FTIR and cyclic voltammetry (CV) while the detection process was carried out by using electrochemical impedance spectroscopy (EIS) analyses. The created immunosensor showed two linear fittings (R2=0.999) for the detection of rh IL‐10 within the concentration range from 1–50 pg/mL. It exhibited high sensitivity (0.1128 (pg/mL)?1) with a very low limit of detection (LOD)=0.347 pg/mL, more particularly, at the low concentration range (1–10 pg/mL). Thus, this developed polypyrrole‐based immunosensor represents a promising strategy for creation of miniaturized label‐free, fast and highly sensitive biosensors for diagnosis of inflammation biomarkers at very low concentrations with reduced cost. 相似文献
12.
G. García J. Silva-Chong J. L. Rodríguez E. Pastor 《Journal of Solid State Electrochemistry》2014,18(5):1205-1213
The electrochemical behavior of acetaldehyde on palladium and platinum electrodes in acidic media was comparatively studied by means of differential electrochemical mass spectrometry (DEMS) and in situ Fourier transform infrared spectroscopy (FTIRS) combined with cyclic voltammetry. It was observed that acetaldehyde decomposition depends on the catalyst material, applied potential, and reactant concentration. Additionally, it was detected that acetaldehyde adsorbs and dissociates at potentials lower than 0.60 V vs RHE, producing methane and adsorbed CO on Pd; while C2-species, CHx and COad are formed on Pt. Besides carbon dioxide, acetic acid and adsorbed acetate were observed at E?>?0.6 V, and their contribution increased with acetaldehyde concentration. Differences between Pt and Pd in potential dependence of the products and intermediates were established. Calibration of the mass spectrometer, together with the use of labeled acetaldehyde and IR spectra, allows establishment of the nature of adsorbed species and products for both Pt and Pd at different potentials, elucidating global reaction pathways for acetaldehyde on these two noble metals. 相似文献
13.
The elementary steps of the anodic oxidation of ethanol on Pt in sulfuric acid are visualized with differential electrochemical mass spectroscopy (DEMS) by means of deuterium and 18O labelling. It turns out that: (i) ethanol is oxidized directly to acetaldehyde by the cleavage of one hydrogen of the α-C-atom and the hydroxyl hydrogen; (ii) a strongly bound intermediate is formed in parallel; (iii) the intermediate is oxidized at 0.7 V to give two CO2 molecules, one originating from the alcoholic group and still containing the alcoholic O, the other from the methyl group; (iv) CC bond splitting seems to occur during the oxidation of the adsorbate only. 相似文献
14.
Electrochemical impedance probing of DNA hybridisation on oligonucleotide-functionalised polypyrrole
We report a new approach for detecting DNA hybridisation using non faradaic electrochemical impedance spectroscopy. The technique was applied to a system of DNA probes bearing amine groups that are immobilized by covalent grafting on a supporting polypyrrole matrix functionalised with activated ester groups.The kinetics of the attachment of the ss-DNA probe was monitored using the temporal evolution of the open circuit potential (OCP). This measurement allows the determination of the time necessary for the chemical reaction of ss-DNA probe into the polypyrrole backbone.The hybridisation reactions with the DNA complementary target and non complementary target were investigated by non faradaic electrochemical impedance spectroscopy. Results show a significant modification in the Nyquist plot upon addition of the complementary target whereas, in presence of the non complementary target, the Nyquist plot is not modified. The spectra, in the form of Nyquist plot, were analysed with the Randles circuit. The transfer charge resistance R2 shows a linear variation versus the complementary target concentration. Sensitivity and detection limit (0.2 nM) were determined and detection limit was lower of one order of magnitude than that obtained with the same system and measuring variation of the oxidation current at constant potential. 相似文献
15.
Polymerization of pyrrole onto the electrode surfaces of thickness-shear-mode acoustic wave sensors at various levels of oxidation has been performed with electrochemical methods. The resulting films of polypyrrole have been characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. Frequency decreases for the polypyrrole-coated sensors exposed to methanol, toluene and ammonia have been evaluated in terms of the various interactions occurring at the polymer surface. 相似文献
16.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1993,49(10):1487-1494
The cw resonance Raman spectra of the products of electrochemical oxidation of 4-(N,N-dialkylamino)biphenyl compounds, with alkyl = methyl, methyl-d3 or ethyl, are analyzed and compared with the time-resolved resonance Raman spectra of the photogenerated radical cation of these amines. The anodic oxidation is shown to lead to the formation of the respective N,N,N′,N′-tetraalkylbenzidine radical cation and dication, and a mechanism scheme for the oxidation is proposed. 相似文献
17.
Nitric acid is manufactured by oxidizing ammonia where the ammonia comes from an energy demanding and non-eco-friendly, Haber–Bosch process. Electrochemical oxidation of N2 to nitric acid using renewable electricity could be a promising alternative to bypass the ammonia route. In this work, we discuss the plausible reaction mechanisms of electrochemical N2 oxidation (N2OR) at the molecular level and its competition with the parasitic oxygen evolution reaction (OER). We suggest the design strategies for N2 oxidation electro-catalysts by first comparing the performance of two catalysts – TiO2(110) (poor OER catalyst) and IrO2(110) (good OER catalyst), towards dinitrogen oxidation and then establish trends/scaling relations to correlate OER and N2OR activities. The challenges associated with electrochemical N2OR are highlighted.Electrochemical oxidation of N2 to HNO3 (N2OR) is explored in conjunction with parasitic oxygen evolution reaction (OER) on a poor and a good OER catalyst, TiO2 and IrO2. We develop scaling relations to correlate OER and N2OR activities on oxides. 相似文献
18.
William R. Heineman 《Applied biochemistry and biotechnology》1993,41(1-2):87-97
Water-soluble polymers immobilized by gamma radiation have been investigated as a means of developing electrochemical sensors. Enzyme-based sensors for glucose and lactate have been made by immobilizing glucose oxidase and lactate oxidase, respectively, on platinized graphite electrodes. The enzyme is entrapped in a polymeric network of poly(vinyl alcohol) that is formed by gamma radiation crosslinking. Electrodes coated with poly (N-vinylpyrrolidone) and its corresponding monomer and then crosslinked with gamma radiation show an extraction of catecholamines into the polymer film that enhances the analytical signal for their detection by electrochemical oxidation. Poly(dimethyldiallylammonium chloride) spin-coated on a screen-printed electrochemical cell provides sufficient ionic conductivity for the cell to function as a gas sensor for oxygen, which is detected by reduction at a platinum working electrode. 相似文献
19.
A. S. Savenkov O. N. Bliznjuk P. V. Kuznetsov Yu. L. Vyatkin N. Yu. Masalitina 《Russian Journal of Applied Chemistry》2015,88(10):1570-1575
A mathematical model of ammonia oxidation on a platinoid catalyst, taking into account the N2O formation, was developed. The possibilities of lowering the amount of N2O, which is formed as by-product in high-temperature oxidation of ammonia in nitric acid production, are examined. The developed model allows calculation of the reactor for ammonia oxidation using platinoid catalysts of different geometric profiles. 相似文献
20.
Differential electrochemical mass spectroscopy (DEMS) was used to obtain information about the strongly adsorbed intermediate during methanol electrooxidation on platinum in sulfuric acid. It turned out that three electrons are released upon oxidation of one adsorbate molecule to CO2. In the presence of oxygen, however, the number of electrons was determined to be between 2 and 2.5. Therefore CO can be excluded as the intermediate during methanol oxidation. COH seems to be the more likely adsorbate involved in the reaction pathway. 相似文献